path case fixes, and a small shader fix

This repo was linked in IRC and I had to try it out.

I've fixed a lot of paths to correctly reflect the case used in the git repo, to get the build working on case-sensitive filesystems.

I've also made a minor fix to one of the shaders to get it to compile on my GTX 580, in linux with driver 310.19. I'm not sure if this is a driver bug or what, the fix is pretty silly.

After these, everything built and ran fine. Nice!